JERUSALEM — Israel sent aircraft, tanks and ground troops to pummel the Gaza Strip on Friday, killing one Palestinian and injuring 17, a day after Palestinian militants killed an Israeli civilian in a mortar attack.

Prime Minister Ehud Olmert warned that Israel was close to abandoning efforts to bring a truce to the volatile area and was seriously considering a large-scale incursion.

“According to the information we have now, the pendulum is much closer to a decision on a harsh operation,” Olmert said soon after returning from a brief visit to the United States.

Egypt has been trying for months to mediate a cease-fire between Israel and the Gaza’s Islamic militant Hamas rulers.

Tough conditionsBut both sides have set tough conditions for a truce, and Israeli leaders are under pressure at home to respond militarily because the weapons in the hands of Gaza militants have become more deadly.

Four Israelis have been killed this year in rocket and mortar attacks, out of a total of 16 killed since 2004.

Israel has been reluctant to launch a large-scale incursion for fear it would result in the deaths of a large number of Israeli soldiers and Palestinian civilians.

Instead, it has been relying on pinpoint airstrikes and ground raids on militant rocket and mortar operations that have severely disrupted life in southern Israel.

One militant was killed and two were injured early Friday in a gunbattle that erupted after Israeli tanks and bulldozers crossed into central Gaza. The military said its forces entered to prevent rocket launches.

Fifteen Palestinians — some Hamas militants, others civilians — were wounded in a second aerial attack on a Hamas base in northern Gaza later Friday, doctors said. The missiles destroyed a building, witnesses said.

Hamas also fired four rockets toward Israel, the group said. One landed in the rocket-scarred town of Sderot, damaging six cars, the military said.

The latest flareup in violence began Thursday when a Hamas mortar killed an Israeli and injured four others in southern Israel. Israel then sent aircraft after a rocket squad, the military said, but apparently missed their target, killing a 6-year-old Palestinian girl.

Operation reviewedIsrael’s Security Cabinet, a group of ministers with security responsibilities, was to review the pros and cons of a large Israeli operation in Gaza at a meeting Sunday, media reported.

In addition to its military operations against militants, Israel also has blockaded Gaza in an effort to force Hamas to rein in rocket launchers. For months, only humanitarian aid and limited fuel shipments have passed into the territory of 1.4 million people, which Hamas seized in a violent takeover one year ago.

The U.S.-backed Palestinian president, Mahmoud Abbas, still controls the West Bank and is engaged in peace talks with Israel. A large Israeli operation in Gaza could provoke Abbas to call off the negotiations.

Egypt has also sealed shut its Rafah crossing with Gaza, in line with an international policy to isolate Hamas until it renounces violence and recognizes Israel’s right to exist.

Gazans protest closureAbout 9,000 Palestinians marched to the Rafah crossing on Friday to protest the prolonged closure, which has sharply deepened the privation in the already impoverished coastal territory.

“This is a warning, and the last plea — Gaza will not accept anymore closures,” Hamas official Ashraf Abu Daya said.

Egypt deployed anti-riot personnel, special forces, snipers and armored vehicles at the border, and forces were given orders to fire on Palestinians who might breach the border.

In January, Hamas militants knocked down a wall separating Gaza from Egypt. Hundreds of thousands of Palestinians rushed into Egypt to stock up on scarce food, gasoline and other supplies. Egypt resealed the border 12 days.